Expansion anchor

ABSTRACT

An expansion anchor sleeve has a leading portion and a circumferential wall which is circumferentially complete at the leading portion but subdivided into a plurality of longitudinal webs rearwardly of the leading portion. The webs each have two axially adjacent sections the first one of which extends rearwardly from the leading portion and has a greater radial thickness and the second one of which extends rearwardly from the first section and has a lesser radial thickness. At the juncture between the two sections of each web a buckling line is provided and the first portion extends radially outwardly from the longitudinal axis of the sleeve at an acute angle thereto, whereas the second portion extends in substantial parallelism with the longitudinal axis. A screw or similar means is provided for subjecting the sleeve to axial tensile forces to thereby effect radial outward buckling of the two sections of each web with reference to one another.

Umted States Patent [1 1 [111 3,785,241 Fischer 1 Jan. 15, 1974 i 1EXPANSION ANCHOR [76] Inventor: Artur Fischer, Altheimer Str. 219,

Tumlingen, Germany Attorney-Mwhael S. Str1ker [22] Filed: Dec. 3, 1971[57] ABSTRACT [2]] A l N 204,512 An expansion anchor sleeve has aleading portion and a circumferential wall which is circumferentiallycomplete at the leading portion but subdivided into a plu- [30] Fol-mgApphcatmn Pnomy Data rality of longitudinal webs rearwardly of theleading 1970 Germany P 20 60 241-9 portion. The webs each have twoaxially adjacent sections the first one of which extends rearwardly fromU.S- Cl. the leading portion and has a greater radial thickness [5 II.-Cl. and the econd one of extends rearwa dly from Fleld Of Search 70, thefirst section and has a lesser radial thickness At the juncture betweenthe two sections of each web a References cued buckling line is providedand the first portion extends UNITED STATES PATENTS radially outwardlyfrom the longitudinal axis of the 2,255,650 9/1941 Burke 85/71 Sleeve atan acute angle thereto, Whereas the Second 3,174,387 3/1965 Fischerg5/71 portion extends in substantial parallelism with the lon- 2,763,3149/1956 Gill t t 85/70 gitudinal axis. A screw or similar means isprovided 3,461,771 8/1969 Briles 85/ 0 for subjecting the sleeve toaxial tensile forces to 3,340,76l 9/1967 Fischer 85/83 thereby effectradial outward buckling of the two ec- FOREIGN PATENTS 0 APPLICATIONStions of each web with reference to one another.

608,218 9/1948 Great Britain 85/71 6 Claims, 4 Drawing FiguresYATENTEDJAH i 5 ism sum 1 or 2 mam-10m 1 IBM 3; 785; 241

SHEET 2 BF 2 EXPANSION ANCHOR BACKGROUND OF THE INVENTION The presentinvention relates generally to an expansion anchor, and moreparticularly to an expansion anchor of synthetic plastic material foruse in conjunction with hollow walls, thin panels and the like.

Anchors of this type are already known in the art. For instance, theprior art teaches an expansion anchor construction in which a shaft-likehollow portion of the sleeve is provided with six rearwardly extendinglongitudinal webs which are spaced circumferentially and which have atthe trailing end of the sleeve free end portions which are to beaccommodated in a bore hole provided in the lowermost of several platesor panels which are superimposed and connected with one another. Thesewebs have a uniform radial thickness over their entire length and it isintended according to the patent that when a screw is threaded into theshaft and tightened, the webs will fold radially and in circumferentialdirection, to provide at the rear side of the lowermost panel anabutment preventing withdrawal of the sleeve from the hole. Basically,this construction is capable of achieving the intended results; however,experience has shown that the proper radial bending or folding does notalways take place, and certainly does not always take place in each andevery one of the webs in the desired manner. If the device does notoperate perfectly in the intended manner, however, then the abutmentformed by those of the webs which do in fact buckle radially is unevenand will not afford as strong a retentive capability as is desirable. Afurther disadvantage of this possibility is found if the device isextended through a wall board panel, either a panel by itself or a panelforming part of a hollow wall. Such wallboard panels or gypsum panelsare manufactured by various producers, for instance by the NationalGypsum Corporation under the trade name Gold Bond and are used for theerection of dry walls. If the abutment portion is uneven, then it is notuncommon that in the case of such a wallboard panel the abutment portionwill destroy the material (gypsum) surrounding the bore hole at the rearor concealed side of the panel when an axial stress is exerted upon theexpansion anchor, and the expansion anchor may thus be drawn out of thebore hole, with simultaneous destruction of the material of the panelwhich surrounds the bore hole. Finally, an additional difficulty whichmay occur is that one or more of the webs will simply fold over in whichcase the danger of damage to the material of the panel in the immediatevicinity of the bore hole opening at the concealed side of the panel isincreased even further.

SUMMARY OF THE INVENTION It is a general object of the present inventionto overcome the disadvantages of the prior art.

More particularly it is an object of the present invention to provide animproved expansion anchor of the type here under discussion, which isnot possessed of these disadvantages.

A further object of the invention is to provide such an improvedexpansion anchor in which it is assured that the webs thereof willbuckle only at a precisely predetermined location and only in radiallyoutward direction.

Another object of the invention is to provide such an expansion anchorwherein at least the expansion anchor sleeve is of synthetic plasticmaterial and wherein, further, the axially directed tensile stresseswhich must be exerted in order to obtain the buckling of the webs is aslow as possible.

The invention meets theseobjects, and others which will become apparenthereafter by providing, according to one embodiment an expansion anchorwhich briefly stated comprises an expansion anchor sleeve having aleading portion and a circumferential wall which is circumferentiallycomplete in the region of the leading portion and circumferentiallysubdivided into a pluralityof longitudinal webs rearwardly of theleading portion. Each of the webs has a first section of greater radialthickness extending rearwardly from the leading portion at an acuteangle to the longitudinal axis of the sleeve and a second section oflesser radial thickness extending rearwardly from the second section inat least substantial parallelism with the longitudinal axis. The firstand second sections of each web form a juncture at which the sectionsare to buckle and fold radially outwardly in response to exertion ofaxial tensile forces and whereat the greater thickness decreases to thelesser thickness. There is further provided means for exerting suchaxially directed tensile forces on the sleeve.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbest be understood from the following description of specificembodiments when read in con nection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial section illustratingthe sleeve of one embodiment of the invention prior to radial bucklingof the webs;

FIG. 2 illustrates the embodiment of FIG. 1 in mounted condition, withthe mounting operation partly completed;

FIG. 3 is an axial section illustrating a further embodiment of theinvention; and

FIG. 4 is a perspective view illustrating an embodiment of the inventionin assembled condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing firstly theembodiment in FIGS. 1 and 2, it will be seen that here the expansionanchor utilizes an expansion anchor sleeve S which preferably is ofsynthetic plastic material. It has the leading portion or shaft 1provided with a central passage 2 which has an internal thread 3.Extending rearwardly from the portion 1 is a plurality of webs 4 havingfree ends 5 which in operation of the anchor, are to become lodged inthe bore hole 6 of one or several superimposed plates or panels 7, asclearly shown in FIG. 2.

In accordance with the present invention the radial thickness of thewebs 4 decreases from a greater radial width of the section 8 of eachweb 4 to a lesser radial width of the associated section 9 of the sameweb 4. At the juncture between each section 8 and 9 of a web 4, that isthe location where buckling is subsequently to take place and which isidentified with reference numeral (compare especially FIG. 2), the innerside of each of the webs 4 is provided with a step 11 which in theillustrated embodiment is tapered, that is decreases gradually at thestep 11.

It is to be noted that the sections 8 extend rearwardly away from theportion 1 at an acute angle outwardly from the longitudinal axis 12 ofthe sleeve S to the juncture 10; from the juncture 10 the sections 9extend in substantial parallelism with the\ axis 12 and are provided attheir rear free ends with radially outwardly directed flange portions 13which contact the outer surface of the plate or panel in which thedevice is to be anchored, or of the outermost plate or panel 7 as shownin FIG. 2.

FIG. 2 indicates that when a screw 14 is threaded from the rear end intothe portion 1 of the device, the shaft portion 1 is drawn in directiontowards the panel or panels 7; as a result of this application of axialtensile forces upon the sleeve the webs 4 will buckle at the junctures10 and move in radially outward direction with simultaneous axialfolding. The sections 9 of lesser thickness will abut in planarorientation against the juxtaposed side of the panel or panels 7, andthe thicker sections 8 will become supported by abutment against thesections 9. With this construction (see FIG. 2) the danger of damage tothe material of the panel or panels 7, especially in the regionsurrounding the hole in which the anchor is mounted, is avoided.

It is clear that the location where buckling will occur, that is at thejuncture 10, is precisely predetermined and, further, that it isimpossible for buckling to occur in any direction other than radiallyoutwardly. Of course, as shown in FIG. 1, before the device is insertedinto a hole provided in panel or panels 7, the free ends (which areprovided with the flange portions 13) will project slightly radiallyoutwardly beyond the normal diameter of a bore hole in which the deviceis to be mounted; when the device is subsequently inserted into such abore hole, the free ends are radially compressed, pivoting about thepoints or locations 10 which are thus located on a circumferential linethe diameter of which is greater than any other diametral distance ofthe sleeve (with the exception of the flange portions 13). This meansthat the sections 8 and 9 both are inclined towards the respective point10 so that absolute assurance exists that buckling in radially outwarddirection will take place at the points 10.

Upon subsequent expansion as shown in FIG. 2, forces transmitted by thesections 8 will act upon the portion 1 on the one hand, and uponportions of the panel or panels 7 on the other hand which are removedradially outwardly away from the immediate vicinity of the bore hole, sothat danger of damage to the material immediately surrounding the borehole is precluded. In addition, a drawing-in of the webs into the borehole is also made impossible. All of this results in a low specific loadapplied to the surface area of the panel in the vicinity of the borehole, and this is of course of significant advantage if the panel is oneof the aforementioned wallboard panels which are highly sensitive tothis type of stress.

Because the sections 9 are compressed radially inwardly towards oneanother when the device is inserted into the bore hole preparatory toexpansion, they engage the inner surface of the bore hole with a springaction, and this provides an increased protection against undesiredturning of the sleeve S in the bore hole when the screw 14 is threadedinto the sleeve.

The sleeve is advantageously made of synthetic plastic material, forinstance by injection molding, and the dies required for this purposecan be relatively simple and inexpensive, so that the production of thissleeve is itself highly economical.

The number of webs 4 may vary depending upon particular requirements. Ingeneral use, it will be found advantageous to use four of them for asleeve S. However, in particular if the outer diameter of the sleeve Sis small, it is advantageous to provide only two rather than four of thewebs 4. They will then have an almost semi-circular shell-shapedcross-section and will of course be considerably wider incircumferential direction of the sleeve S than would be the case ifthere were four of them. Because of this they are relatively stiff andthis in turn permits them to terminate the drawing of the device towardsthe panel in axial direction, and thereby the radial buckling of thewebs at a location or time at which the thicker or greater-thicknesssections of the respective webs are still inclined at an acute anglewith respect to the longitudinal axis of the sleeve. In this case theaxial load acting upon the anchor mounted in a panel or the like, willbe supported in a pillar-like manner at the rear side of the panel viathe buckling locations 10 which are remote from the bore hole. Therequirement of this is that the shaft has been drawn far enough towardsthe panel so that the web sections having the lesser radial thicknesswill already be in complete engagement with the panel surface.

FIG. 4 shows such an embodiment which in other respects is the same asthe embodiment of FIGS. 1 and 2. In fact, the same reference numeralshave been used to designate like components as in FIG. 4 and it will beseen that the only difference is in the fact that the sleeve S isprovided with only two rather than four of the webs 4. The greatercircumferential width of these two webs is clearly evident. FIG. 4 ofcourse illustrates the device in already-mounted and expanded condition.

It should be pointed out that if the diameter of the expansion anchorsleeve is relatively great, it will be advisable and perhaps evennecessary to provide four of the webs, because otherwise the resistanceof the webs to buckling would be too great, and as a result too muchaxial tension would be required to effect such buckling. However, if theouter diameter of the expansion anchor sleeve is relatively large, thenit will be appreciated that even if such a sleeve has four rather thanonly two of the webs 4, the effect (in terms of strength of each web)will be approximately the same as in smaller-diameter sleeves havingonly two of the webs. Understandably, the flange protions 13 illustratedin FIGS. 1 and 2 need not be provided. However, they are advantageousbecause it makes it possible to insert the sleeve into a bore holewithout previously inserting the screw 14 into the sleeve, at the sametime affording protection against the possibility that during subsequentinsertion of the screw into the sleeve the latter might be pushed out ofthe hole and through the panel to the rear thereof.

It is particularly advantageous if the expansion anchor according to thepresent invention is additionally constructed as a conventionalexpansion anchor, which may have an elongated sleeve portion extendingrearwardly from its leading end. Such an embodiment is illustrated byway of example in FIG. 3 where the same reference numerals have beenemployed as in the preceding Figures for like elements. In thisembodiment the shaft 1 is configurated as a known expansion anchorsleeve which is to be anchored in the bore hole 16 of a wall, forinstance a masonry wall 17.

It should be noted that here the free ends of the ribs 4, or rather ofthe sections 19 thereof, are configurated so that they can beaccommodated to the bevelled head 19 of a screw 20, with the bevelindicated at reference numeral 18. The panel 7 of FIG. 2 is herereplaced by a cladding plate 21 which is to be mounted on masonry wall17 with some spacing therefrom. For this purpose the entire expansionanchor is passed through a bore 22 into the plate 21 into the bore 16 ofthe wall 17, to such an extent that the cladding plate 21 becomespositioned at a desired distance from the exposed surface of the wall17, increased by the extent to which the webs 4 can be axially collapsedwhen they buckle radially. When thereupon the screw is threaded into theshaft 1, the expansion anchor portion 15 is spread radially in the bore16, anchoring the sleeve in the wall 17. On the other hand the webs 4again become radially buckled in the manner discussed earlier and alsobecome axially collapsed. As a result of this the sections 9 again abutthe concealed side of the panel 21 and the sections 8 provide for thedesired retention of the panel 21 against movement with reference to thewall 17.

This embodiment serves primarily, as already indicated, to anchorcladding plates or panels 21 at a certain distance from a surface onwhich they are to be mounted, for instance from the exposed surface ofthe wall 17. Of course, the embodiment can also be utilized for otherpurposes; it has the advantage that it makes it possible to provide forsmall adjustments of the distance of the panel 21 from the surface ofthe wall 17 without having to release the anchor which has already beenanchored in the hole 16 of the wall 17. When the screw 20 is tightened,the radial buckling of the webs 4 begins as soon as the head 19 of thescrew 20 has entered into the recessed bore of the panel 21 and exertsan axial force thereon; further turning of the screw 20 is terminatedwhen the panel is spaced at the desired distance from the wall 17.

FIG. 3 further shows that if desired the outer sides of the webs 4, orat least some of them, can be provided with ribs R which extend over atleast part of the length of the webs 4, namely that part which is to belocated within the bore hole of a panel or plate. Of course, the ribs Rneed not be provided, but if provided they serve to provide addedassurance against undesired turning of the sleeve when the screw isbeing tightened. On the other hand they further have the advantage thaton insertion of the sleeve through the bore hole they cause the freeends of the webs 4 to be pushed radially inwardly to such an extent thatthey contact one another in circumferential direction, whereby thesleeve will be tightly retained in a bore hole without freedom of play,even before the screw is inserted and tightened.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in anexpansion anchor, it is not intended to be limited to the details shown,since various modifications and structural changes may be made 5 withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in particular in the appended claims.

I claim:

1. An expansion anchor, comprising an expansion anchor sleeve having aleading portion, and a circumferential wall which is circumferentiallycomplete in the region of said leading portion and circumferentiallysubdivided into a plurality of longitudinal webs rearwardly of saidleading portion, said webs each being of part-circular cross-section andeach including a first section of a substantially constant radialthickness extending rearwardly from said leading portion at an acuteangle to the longitudinal axis of said sleeve, and a second section of asubstantially constant lesser radial thickness than said first sectionextending rearwardly from said first section in at least substantialparallelism with said longitudinal axis, said first and second sectionsof each web forming an abrupt juncture at which said sections are tobuckle and fold radially outwardly in response to exertion of axialcompressive forces and at which said thickness of said first sectiondecreases to said lesser thickness of said second section, and each ofsaid second sections having an end portion rearwardly spaced from saidjuncture and which is free of connection with the respective endportions of the other ones of said second sections; and means forengaging said leading portion and for exerting axially directedcompressive forces on said sleeve.

2. An expansion anchor as defined in claim 1, wherein said sleeve is ofsynthetic plastic material.

3. An expansion anchor as defined in claim 1, wherein the radialthickness of each web tapers at said junction from said greater to saidlesser thickness.

4. An expansion anchor as defined in claim 1, said sleeve furthercomprising a forward portion forwardly of said leading portion andcomposed of at least two elongated expansible jaws adapted to beradially expanded.

5. An expansion anchor as defined in claim 1, wherein each of said endportions is provided with a flange portion extending in directionradially outwardly of said sleeve.

6. An expansion anchor as defined in claim 1; further comprising ribsprovided on the outer side of said webs over at least a protion of thelength of the latter.

1. An expansion anchor, comprising an expansion anchor sleeve having aleading portion, and a circumferential wall which is circumferentiallycomplete in the region of said leading portion and circumferentiallysubdivided into a plurality of longitudinal webs rearwardly of saidleading portion, said webs each being of part-circular cross-section andeach including a first section of a substantially constant radialthickness extending rearwardly from said leading portion at an acuteangle to the longitudinal axis of said sleeve, and a second section of asubstantially constant lesser radial thickness than said first sectionextending rearwardly from said first section in at least substantialparallelism With said longitudinal axis, said first and second sectionsof each web forming an abrupt juncture at which said sections are tobuckle and fold radially outwardly in response to exertion of axialcompressive forces and at which said thickness of said first sectiondecreases to said lesser thickness of said second section, and each ofsaid second sections having an end portion rearwardly spaced from saidjuncture and which is free of connection with the respective endportions of the other ones of said second sections; and means forengaging said leading portion and for exerting axially directedcompressive forces on said sleeve.
 2. An expansion anchor as defined inclaim 1, wherein said sleeve is of synthetic plastic material.
 3. Anexpansion anchor as defined in claim 1, wherein the radial thickness ofeach web tapers at said junction from said greater to said lesserthickness.
 4. An expansion anchor as defined in claim 1, said sleevefurther comprising a forward portion forwardly of said leading portionand composed of at least two elongated expansible jaws adapted to beradially expanded.
 5. An expansion anchor as defined in claim 1, whereineach of said end portions is provided with a flange portion extending indirection radially outwardly of said sleeve.
 6. An expansion anchor asdefined in claim 1; further comprising ribs provided on the outer sideof said webs over at least a portion of the length of the latter.